Dielectric response of Ba0.75Sr0.25TiO3 epitaxial films to electric field and temperature (original) (raw)
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The ferroelectric behavior of Ba 0.75 Sr 0.25 TiO 3 (BST) thin films deposited on nichrome substrates by RF-Sputtering sintered in situ at 673-1023 K temperature range has been studied. The thin films microstructures were observed using atomic force microscopy to determine rugosity and grain size. Extensive grain growth was observed at temperatures of 822 and 1023 K, varying from 75 to 95 nm, respectively. The ferroelectric properties were determined by the hysteresis loops applying an electric field of 100 kV/cm. The films sintered in the temperature range of 822-1023 K show a reduction of the remnant polarization Pr from 9.87 o C/cm 2 to 2.23 o C/cm 2 , and the coercive field strength E c decrease from 57.75 kV/cm 2 to 19.85 kV/cm 2 . In situ heat treatments let to have more uniform grain size distribution, and relative low rugosities.
Applied Physics Letters, 2009
Ba x Sr 1−x TiO 3 is ideally suited as a tunable medium for radio frequency passive component. In this context we have studied the effect of biaxial strain on the dielectric and ferroelectric properties of Ba 0.5 Sr 0.5 TiO 3 thin films grown epitaxially on SrTiO 3 ͑001͒ substrates. The lattice parameters of the films determined by high-resolution x-ray diffraction with the thickness varying from 160 to 1000 nm indicated large biaxial compressive strain which decreased from 2.54% to 1.14% with increasing film thickness. Temperature-dependent measurements of the dielectric constant in our strained Ba 0.5 Sr 0.5 TiO 3 thin films revealed a significant increase in the Curie temperature as the film thickness is below 500 nm. Enhanced ferroelectric behavior was observed for highly strained films with a remanent polarization of 15 C / cm 2 in the 160-nm-thick layer. However, the thick films ͑Ն500 nm͒ exhibited weak temperature dependence of the dielectric constant without any pronounced peak corresponding to the Curie temperature, which may suggest inhomogeneous strain distribution in the thick films.
Dielectric properties of ferroelectric (Ba0.6Sr0.4)TiO3 thick films prepared by tape-casting
Journal of Electroceramics, 2006
Thick BST films have been fabricated by a tape casting and firing method. Dielectric constants of BST films are changed from 5700 to 7000 at 1 MHz after focused beam annealing. Furthermore, surface morphologies and depth profile of chemistry have been altered after annealing. Especially, Sr atoms diffuse out to the surface, while Ba atoms diffuse into the center. The possibility of the surface alteration of the thick films have been clearly demonstrated in this study, which may applied for the integration of ferroelectrics and other dielectrics and/or conductors for low cost microwave tunable devices.
Applied Physics Letters, 1995
The primary objective of this research is to optimize the different deposition conditions to obtain high tunability and low dielectric loss of Barium Strontium Titanate (BST) thin films at microwave frequencies. Ba 0.5 Sr 0.5 TiO 3 thin films were deposited on Pt/TiO 2 /SiO 2 /Si substrates by pulsed laser deposition technique (PLD). Deposition conditions like temperature, oxygen pressure, substrate to target distance and laser energy are varied to obtain the objective. Deposition of the BST thin films on the Pt/TiO 2 /SiO 2 /Si substrates was carried out at temperatures of 450ºC, 550°C, 650ºC and oxygen pressures of 250mTorr and 450mTorr with laser fluence of 250 mJ/cm 2 and 450mJ/cm 2 at 10 pulses per second. The microstructural and phase analysis of the deposited BST films at different temperatures and different oxygen pressures were performed using X-ray diffraction (XRD) method. The diffraction patterns are attributed to cubic (perovskite) crystal system. Atomic force microscopy (AFM) was used to perform the surface analysis of the films deposited at different substrate to target distances, varied laser energies and oxygen pressures. The BST capacitor was fabricated using the Coplanar Waveguide Structure and the capacitance and dielectric constant were measured using the Vector Network Analyzer (VNA). Tunability of 3.1:1 and loss tangent of 0.0121 was achieved at 0.4-0.8 GHz.
Integrated Ferroelectrics, 2008
The dielectric properties of barium strontium titanate thin films with composition Ba 0.6 Sr 0.4 TiO 3 were studied as a function of film thickness for implementation in a variety of devices with different requirements. Films were prepared by metalorganic solution deposition and characterized using scanning electron microscopy, atomic force microscopy, and Rutherford back-scattering. The dielectric (100 kHz) and insulating properties were also measured. The film morphology and dielectric/insulating properties are thickness dependent, yet the best combination of properties was in films of 160 nm to 240 nm. These films had a moderate dielectric constant (∼300), low loss (∼0.029), good tunability (∼30%), and low leakage current (∼10 −8 A/cm 2).
Japanese Journal of Applied Physics, 2002
Pristine, W and Mn 1% doped Ba 0.6 Sr 0.4 TiO 3 epitaxial thin films grown on the LaAlO 3 substrate were deposited by pulsed laser deposition (PLD). Dielectric and ferroelectric properties were determined by the capacitance measurements and X-ray diffraction was used to determine both residual elastic strains and defect-related inhomogeneous strains by analyzing diffraction line shifts and line broadening, respectively. We found that both elastic and inhomogeneous strains are affected by doping. This strain correlates with the change in Curie-Weiss temperature and can qualitatively explain changes in dielectric loss. To explain the experimental findings, we model the dielectric and ferroelectric properties of interest in the framework of the Landau-Ginzburg-Devonshire thermodynamic theory. As expected, an elastic-strain contribution due to the epilayer-substrate misfit has an important influence on the free-energy. However, additional terms that correspond to the defect-related inhomogeneous strain had to be introduced to fully explain the measurements.
Electrical Properties of Crystalline Ba0.5Sr0.5TiO3 Thin Films
2001
Thin Ba0.5Sr0.5TiO3 (BST) films on p-type Si (100) using The Chemical Solution Deposition (CSD) method. X-ray diffraction (XRD), Scanning electron microscopy (SEM), C-V meter analysis measurement were employed to characterise the films. The growth condition to obtain enough quality epitaxial of Ba0.5Sr0.5TiO3 carried out by spin coating at 3000 rpm for 30 seconds, and then annealing at 900oC for 15 hours. The structure and crystallinity of thin films were investigated by XRD preffered orientation (100), (010); (110), (111), (200), surface analysis by SEM magnification x10000 thin films were heterogen and thickness film 1100 nm; electrical characterization Ba0.5Sr0.5TiO3 at MFS (Metal Ferroelectric Semiconductor) structure in room temperature (300 K) by carried out capacitance flat band (CFB) for frequency 10 KHz and 100 KHz were 206 pF and 187 pF, dielectric constant for frequency 10 KHz and 100 KHz were 132.67 and 117.22, dielectric loss minimum for frequency 10 KHz and 100 KHz were 5.37 % and 6.43 % respectively.
Thin Solid Films, 2001
. Polycrystalline Ba Sr TiO xs 0.4 and 0.8 thin films with a perovskite structure were prepared by the polymeric precursor x 1yx 3 method on a platinum-coated silicon substrate. High-quality thin films with uniform composition and thickness were successfully produced by dip-coating and spin-coating techniques. The resulting thin films prepared by dip and spin-coating showed a well-developed dense polycrystalline structure with uniform grain size distribution. The metal᎐BST-metal structure of the thin Ž . films displays good dielectric and ferroelectric properties. The ferroelectric nature to Ba Sr TiO xs 0.8 thin film, indicated x 1yx 3 by butterfly-shaped C᎐V curves and confirmed by the hysteresis curve, showed 2 P s 5.0 Crcm 2 and E s 20 kVrcm. The r c capacitance᎐frequency curve reveals that the dielectric constant may reach a value of up to 794 at 1 kHz. On the other hand, the Ž . Ba Sr TiO x s 0.4 thin films had paraelectric nature and dielectric constant and the dissipation factor at a frequency of 100 x 1yx 3 kHz were 680 and 0.01, respectively, for film annealed at 700ЊC. In addition, an examination of the film's I᎐V curve at room Ž . temperature revealed the presence of two conduction regions in the Ba Sr TiO xs 0.4 and 0.8 thin films, showing x 1yx 3
Frequency Dependent Electrical Properties of Ferroelectric Ba0.8Sr0.2TiO3 Thin Film
The frequency dependent electrical parameters, such as impedance, electric modulus, dielectric constant and AC conductivity for ferroelectric Ba0.8Sr0.2TiO3 thin film have been investigated within the range of 1 Hz and 106 Hz at room temperature. Z* plane shows two regions corresponding to the bulk mechanism and the distribution of the grain boundaries-electrodes process. M" versus frequency plot reveals a relaxation peak, which is not observed in the ε″ plot and it has been found that this peak is a non-Debye-type. The frequency dependent conductivity plot shows three regions of conduction processes, i. e., a low-frequency region due to DC conduction, a mid-frequency region due to translational hopping motions and a high-frequency region due to localized hopping and/or reorientational motion.